Protozoa: Structure, Classification, and Development PDF

Protozoa: Structure, Classification, Development, Species, Parasitism Lecture Study Program: Veterinary Medicine Subject: Life Sciences I / Plant Biology, Zoology and Laboratory Animals ...

Protozoa: Structure, Classification, Development, Species, Parasitism Lecture Study Program: Veterinary Medicine Subject: Life Sciences I / Plant Biology, Zoology and Laboratory Animals  Major Divisions of Life Whittaker’s five-kingdom classification superimposed on a phylogenetic tree showing living representatives of these kingdoms. https://biocyclopedia.com/index/general_zoology/major_divisions_of_life.php  Protozoa The Protozoa are considered to be a subkingdom of the kingdom Protista. Protozoan biodiversity (or species richness) includes counts (or estimates) of some 32,000 extant (living) species (some authors counts more than 50,000 species) and another 34,000 extinct (fossil) species (especially Foraminifera). Of those alive today, some 21,000 species occur as free-living organisms in aquatic or terrestrial environments, whereas the remaining 11,000 species are parasitic in vertebrate and invertebrate hosts. There are approximately 6,900 flagellate species (1,800 parasitic, 5,100 free-living), 11,550 amoebae species (250 parasitic, 11,300 free-living), 7,200 ciliate species (2,500 parasitic, 4,700 free-living) and 5,600 sporozoan species (all parasitic).  Structure Most protozoa are microscopic organisms, only a few grow to a size large enough to be visible to the naked eye. Protozoa are unicellular eukaryotes. As in all eukaryotes, the nucleus is enclosed in a membrane. As unicellular eukaryotes, protozoa display all the same essential life activities as higher metazoan eukaryotes: they move about to survive, feed and breed. The organelles of protozoa have functions similar to the organs of higher animals. The plasma membrane enclosing the cytoplasm also covers the projecting locomotory structures such as pseudopodia, cilia, and flagella. The outer surface layer of some protozoa, termed a pellicle, is sufficiently rigid to maintain a distinctive shape.  Structure In most protozoa the cytoplasm is differentiated into ectoplasm (the outer, transparent layer) and endoplasm (the inner layer containing organelles); the structure of the cytoplasm is most easily seen in species with projecting pseudopodia, such as the amebas. Some protozoa have a cytosome or cell “mouth” for ingesting fluids or solid particles. Contractile vacuoles for osmoregulation occur in some, such as Naegleria and Balantidium. Many protozoa have subpellicular microtubules; in the Apicomplexa, which have no external organelles for locomotion, these provide a means for slow movement. The trichomonads and trypanosomes have a distinctive undulating membrane between the body wall and a flagellum. Many other structures occur in parasitic protozoa, including the Golgi apparatus, mitochondria, lysosomes, food vacuoles, conoids in the Apicomplexa, and other specialized structures. From the point of view of functional and physiologic complexity, a protozoan is more like an animal than like a single cell.  Nutrition The nutrition of all protozoa is holozoic; that is, they require organic materials, which may be particulate or in solution. Amebas engulf particulate food or droplets through a sort of temporary mouth, perform digestion and absorption in a food vacuole, and eject the waste substances. Many protozoa have a permanent mouth, the cytosome or micropore, through which ingested food passes to become enclosed in food vacuoles. Pinocytosis is a method of ingesting nutrient materials whereby fluid is drawn through small, temporary openings in the body wall. The ingested material becomes enclosed within a membrane to form a food vacuole.  https://www.enchantedlearning.com/paint/subjects/protists/amoeba.shtml Nutrition AUTOTROPHIC HETEROTROPHIC MYXOTROPHIC Phagocytosis „Photosynthesis“ (day) Photosynthesis Pinocytosis Heterotrophic (night)  Reproduction Reproduction in the Protozoa may be asexual or both asexual and sexual. The most common type of asexual multiplication is binary fission, in which the organelles are duplicated and the protozoan then divides into two complete organisms. Division is longitudinal in the flagellates and transverse in the ciliates; amebas have no apparent anterior-posterior axis. In schizogony, a common form of asexual division, the nucleus divides a number of times, and then the cytoplasm divides into smaller uninucleate merozoites. In Plasmodium, Toxoplasma, and other apicomplexans, the sexual cycle involves the production of gametes (gamogony), fertilization to form the zygote, encystation of the zygote to form an oocyst, and the formation of infective sporozoites (sporogony) within the oocyst.  Reproduction Some protozoa have complex life cycles requiring two different host species; others require only a single host to complete the life cycle. A single infective protozoan entering a susceptible host has the potential to produce an immense population. However, reproduction is limited by events such as death of the host or by the host's defense mechanisms, which may either eliminate the parasite or balance parasite reproduction to yield a chronic infection.  Life Cycle Stages During its life cycle, a protozoan generally passes through several stages that differ in structure and activity. Trophozoite is a general term for the active, feeding, multiplying stage of most protozoa. In parasitic species this is the stage usually associated with pathogenesis. In the hemoflagellates the terms amastigote, promastigote, epimastigote, and trypomastigote designate trophozoite stages that differ in the absence or presence of a flagellum and in the position of the kinetoplast associated with the flagellum. Other stages in the complex asexual and sexual life cycles seen in this phylum are the merozoite (the form resulting from fission of a multinucleate schizont) and sexual stages such as gametocytes and gametes. Some protozoa form cysts that contain one or more infective forms.  Life Cycle Stages Multiplication occurs in the cysts of some species so that excystation releases more than one organism. For example, when the trophozoite of Entamoeba histolytica first forms a cyst, it has a single nucleus. As the cyst matures nuclear division produces four nuclei and during excystation four uninucleate metacystic amebas appear. Similarly, a freshly encysted Giardia lamblia has the same number of internal structures (organelles) as the trophozoite. However, as the cyst matures the organelles double and two trophozoites are formed. Cysts passed in stools have a protective wall, enabling the parasite to survive in the outside environment for a period ranging from days to a year, depending on the species and environmental conditions. Cysts formed in tissues do not usually have a heavy protective wall and rely upon carnivorism for transmission. Oocysts are stages resulting from sexual reproduction in the Apicomplexa. Some apicomplexan oocysts are passed in the feces of the host, but the oocysts of Plasmodium, the agent of malaria, develop in the body cavity of the mosquito vector.  Life-cycles To move from host-to-host, protozoan parasites use one of four main modes of transmission: direct, faecal-oral, vector-borne and predator-prey transmission. https://parasite.org.au/para-site/contents/protozoa-intoduction.html  direct transmission of trophozoites through intimate body contact, such as sexual transmission (e.g. Trichomonas spp. flagellates causing trichomoniasis in humans and bovine infertility in cattle). https://parasite.org.au/para-site/contents/protozoa-intoduction.html  faecal-oral transmission of environmentally-resistant cyst stages passed in faeces of one host and ingested with food/water by another (e.g. Entamoeba histolytica, Giardia duodenalis and Balantidium coli all form faecal cysts which are ingested by new hosts leading to amoebic dysentery, giardiasis and balantidiasis, respectively). https://parasite.org.au/para-site/contents/protozoa-intoduction.html  vector-borne transmission of trophozoites taken up by blood-sucking arthropods (insects or arachnids) and passed to new hosts when they next feed (e.g. Trypanosoma brucei flagellates transmitted by tsetse flies to humans where they cause sleeping sickness, Plasmodium spp. haemosporidia transmitted by mosquitoes to humans where they cause malaria). https://parasite.org.au/para-site/contents/protozoa-intoduction.html  predator-prey transmission of zoites encysted within the tissues of a prey animal (e.g. herbivore) being eaten by a predator (carnivore) which subsequently sheds spores into the environment to be ingested by new prey animals (e.g. tissue cysts of the sporozoan Toxoplasma gondii being ingested by cats, and tissue cysts of the microsporan Thelohania spp. being ingested by crustaceans). https://parasite.org.au/para-site/contents/protozoa-intoduction.html  Taxonomic overview Kingdom. Protozoa Ph. Sarcodina Ph. Mastigophora Ph. Sporozoa (Apicomplexa) Ph. Microsporidia Ph. Cnidosporidia Ph. Ciliophora  Phylum. Sarcodina Order. Amoebida Order. Testacea Order. Foraminifera Sarcodines are known for not having a definite body shape. They are amoeboid forms which may be free living or parasitic. The sarcodines are known for developing temporary projections of the protoplasm, called pseudopodia, which help in locomotion and food capturing. The body usually does not have a pellicle. The cytoplasm may be uninucleate or binucleate or multinucleate. Nutrition is holozoic or parasitic. Asexual reproduction is most common. It occurs by binary fission or multiple fission or in some cases, by spore formation. Sexual reproduction may involve isogamy or anisogamy.  Order. Amoebida There are many entozoic amebas, most of which live in the intestines of humans or other animals. Two common genera are Endamoeba and Entamoeba. Endamoeba blattae is the endocommensal in the intestine of cockroaches, and related species are found in termites. Other species of Entamoeba found in humans are E.coli in the intestine and E. giginvalis in the mouth. Neither of these species is known to cause disease. Human parasitic amoeba Entamoeba histolytica is the most important parasite in humans. It lives in the large intestine and on occasion can invade the intestinal wall by secreting enzymes that attack the intestinal lining. If this occurs, a serious and sometimes fatal amebic dysentery may result. The organisms may be carried by the blood to the liver and other organs and cause abscesses there. Many infected persons show few or no symptomus but are carriers, passing cysts in their feces. Infection is spread by contaminated water or food containing the cysts. Entamoeba histolytica. Life cycle. Top blue arrow shows cysts being ingested. Within the intestine, the cyst produces trophozoites that cause amebic dysentery in the colon and can spread to the liver (most often), lung, and brain (Boxes A and B). Bottom blue arrow shows cysts and trophozoites being passed in the stool and entering the environment. Red arrow indicates survival of cysts in the environment. (Reproduced with permission from Centers for Disease Control and Prevention.) Citation: Chapter 51 Intestinal & Urogenital—Protozoa, Levinson W, Chin-Hong P, Joyce EA, Nussbaum J, Schwartz B. Review of Medical Microbiology & Immunology: A Guide to Clinical Infectious Diseases, 16e; 2020. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=242761584&bookid=2867 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Order. Testacea Some have their delicate plasma membrane covered with a protective test or shell. They have a test of secreted siliceous or chitinoid material that may be reinforced with grains of sand. They move by means of pseudopodia that project from openings in the shell. T – Arcella, Difflugia.  Order. Foraminifera The foraminiferans are an ancient group of shelled found in all oceans, with a few in fresh and brackish water. They are mostly bottom living, but few live in open water. Most tests are many chambered and are made of calcium carbonate, although silica, silt, and other foreign materials are sometimes used. Slender pseudopodia extend through openings in the test, then branch and run together to form a protoplasmic net (reticukopodia) in which they ensnare their prey. Here the captured prey is digested, and the digested products are carried into the interior by the flowing protoplasm.  Phylum. Mastigophora Zooflagellates are unicellular organisms which may be free living or parasitic. Many of them occur as parasites in various hosts. They have an elongated body containing a single, large nucleus. The body is surrounded by a transparent pellicle. One or two flagella are present which are used for locomotion and food capturing. The most common method of reproduction is by binary fission. Some forms exhibit cyst formation. Sexual reproduction is very rare. Subphylum. Phytomastigina Subphylum. Zoomastigina  Subphylum. Phytomastigina Class. Euglenoidina Its natural habitat is freshwater streams and ponds where there is considerable vegetation. Just beneath the outer membrane of Euglena are proteinaceous strips and microtubules that form the pellicle. A flagellum extends from a flask-shaped reservoir at the anterior end, and another, short flagellum ends with in the reservoir. A kinetosome is found at the base of each flagellum, and a contractile vacuole emties into the reservoir. A red eyespot, or stigma, apparently functions in orientation to light. Euglena is autotrophic, but if kept in the dark the organism makes use of saprozoic nutrition, absorbing nutrients through its body surface.  Class. Volvocaceae Volvox is a colonial. The order to which Volvox belongs includes many freshwater flagellates, mostle green, with a cellulose cell wall through which two short flagella project. Volvox cell with nucleus, a pair of flagella, a large chromoplast, and a red stigma. Adjacent cells are connected with each other by cytoplasmic strands. Reproduction is asexual or sexual (macrogametes or microgametes).  Subphylum. Zoomastigina Class. Protomonadina Order. Bodonida It is a single-celled microscopic organism and has two flagella. These are thread-like structures that are used during movement. Found in both a free-living form and a parasitic, feeding form, it can multiply rapidly in both cold and warm water. Ichthyobodo necator is a common parasite that infects a wide range of freshwater fish species. The parasite is found on the skin and gills of fish, most commonly attaching to the edges of the gills. Infected fish have a disease called ichthyobodosis (sometimes known as costiosis).  Class. Protomonadina Order. Trypanosomatids (Trypanosomatida) Trypanosomatids are a group of kinetoplastid protozoa distinguished by having only a single flagellum. All members are exclusively parasitic, found primarily in insects. A few genera have life-cycles involving a secondary host, which may be a vertebrate, invertebrate or plant. These include several species that cause major diseases in humans  Order. Trypanosomatids Trypanosoma occurs as a parasite in human body. It causes the African sleeping sickness. This species lives in the blood of African antelopes that are bitten by the tsetse – fly Glossina palpalis. Trypanososomes, together with blood of the antelope, are transferred into the gut of the insect. In the insect they undergo typical changes in shape while they migrate from the mid gut into salivary glands. If, by bite, transferred into the blood- stream of man, they at first cause Trypanosome fever and subsequently, on entering the cerebro- spinal fluid, sleeping sickness leading to death.  Life cycle of the etiologic agents of sleeping sickness (Trypanosoma gambiense and T. rhodesiense). From Mahon and Manuselis, 2000. http://clem.mscd.edu/~churchcy/BIO3270/Images/Protozoans/Trypanosoma.htm Trypanosoma cruzi T. cruzi causes Chagas disease in humans and animals in America. Transmission occurs when the Triatoma infestans deposits feces on the skin surface and subsequently bites. The symptoms of Chagas disease vary over the course of an infection. It is transmitted by the bite of the “kissing bug” (Triatominae). http://www.cals.ncsu.edu/course/ent425/text18/humanvectors.html www.medicine.mcgill.ca Life cycle of Leishmania They are transmitted by sandflies www.medicine.mcgill.ca Leishmaniasis http://www.umm.edu/imagepages/2656.htm http://www.primehealthchannel.com/category/infectious-diseases/page/2 Visceral leishmaniasis http://drugline.org/medic/term/visceral-leishmaniasis/  Class. Polymastigina Giardia lamblia often causes no disease in the intestine of humans but may sometimes produce severe diarrhea. It is transmitted through fecal contamination. Giardia lamblia. Life cycle. Top blue arrow shows cysts being ingested. Within the intestine, the cyst produces trophozoites that cause diarrhea. Bottom blue arrow shows cysts and trophozoites being passed in the stool and entering the environment. Red arrow indicates survival of cysts in the environment. (Used with permission from Dr. Alexander J. da Silva and Melanie Moser, Centers for Disease Control and Prevention.) Citation: Chapter 51 Intestinal & Urogenital—Protozoa, Levinson W, Chin-Hong P, Joyce EA, Nussbaum J, Schwartz B. Review of Medical Microbiology & Immunology: A Guide to Clinical Infectious Diseases, 16e; 2020. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=242761584&bookid=2867 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Class. Polymastigina Order. Trichomonas (Trichomonatida) Several species of Trichomonas are symbiotic. Trichomonas hominis is found in the cecum and colon of humans and apparently causes no disease. T. vaginalis inhabits the urogenital tract of humans, is transmitted venereally, and may cause vaginitis. Other species of Trichomonas are widely distributed through all classes of vertebrates and many invertebrates. http://www.trichomoniasis.org/Trichomonas_Vaginalis/Index.aspx  Class. Opalinea Opalina is a parasitic protozoan found in digestive system of amphibians. It has a large body covered with cilia. Numerous nuclei (large dots) and mitochondria (little dots) are visible in the cell.  Phylum. Sporozoa These are protozoans which occur as endoparasites in different groups of animals. They lack locomotor structures. The body has a tough covering called cuticle and a single nucleus. Asexual reproduction occurs by multiple fission. Sexual reproduction involves anisogamy. Life cycle may involve more than one host. The most important Phylum, contains two classes: the Gregarinia, the Coccidia. The gregarines are common parasites of invertebrates, but they are of little economic significance. Sporozoa Class. Gregarinina Class. Coccidiomorpha  Class. Coccidiomorpha The Coccidia are intracellular parasites in invertebrates and vertebrates, and the group includes species of very great medical and veterinary importance. Class. Coccidiomorpha Order. Haemosporida Order. Coccidiida  Order. Coccidiida (Coccidiida) Eimeria. The name “coccidiosis” is generally applied only to infections with Eimeria or Isospora. Humans are occasionally infected with species of Isospora, but apparently there is little disease. Some species of Eimeria may cause serious disease in some domestic animals. The symptom is usually severe diarrhea or dysentery. E. tenella is often fatal to young fowl, producing severe pathogenesis in the intestine. The organisms undergo schizogony in the intestinal cells, finally producing gametes. After fertilization the zygote forms an oocyst that passes out of the host in the feces. Sporogony occurs within the oocyst outside the host, producing eight sporozoites in each oocyst. Infection occurs when a new host accidentally ingests a sporulated oocyst and the sporozoites are released by digestive enzymes.  The life cycle of Coccidia (Coccidiida) The life cycle of Coccidias consists of three stages: a) assexual reproduction – schizogony that occurs in the epithelium of human intestine cells; b) sexual reproduction – gametogony, during which microgametas and macrogametas form. After their convergence zygots are formed (host); c) sporogony – formation of oocistas and sporozoites. This process takes place in external environment. Typical life cycle of Coccidia in birds http://www.thepoultrysite.com  Animal Coccidia species: Bovine – Eimeria bovis, E. brasiliensis; Pigs – E. deblecki, Isospora suis; Rabbits – E. stiedai, E. intestinalis, E. magna, E. perforans; Poultry – E. tenella, E. maxima, E. truncata. E. acervulina; Dogs – E. canis; Human – I. belli.  Toxoplasma gondii Toxoplasma. A similar life cycle occurs in Toxoplasma gondii, a parasite of cats, but this species produces extraintestinal stages as well. The extraintestinal stages can develop in a wide variety of animals other than cats – for example, rodents, cattle, and humans. Gametes and oocysts are not produced by the extraintestinal forms, but they can initiate the intestinal cycle in a cat that eats infected prey. Toxoplasmosis. Pathways for Toxoplasma gondii infection: http://www.aafp.org/afp/2003/0515/p2131.html Fig. 1. Toxoplasma gondii life cycle shows oocysts from cat feces or cysts from inadequately cooked meat as infectious to humans and other animals. (Adapted with permission from Nester EW: Microbiology: A Human Perspective, 6th edition. 2009.) Citation: Chapter 51 Apicomplexa and Microsporidia, Ryan KJ. Sherris Medical Microbiology, 7e; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=176089100&bookid=2268 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  There are two types of toxoplasmosis a) acquired, that is common among adults. It manifests by increase of lymph nodes, general weakness, headaches and muscular aches. b) innate, as in organism of a pregnancy period toxoplasmas enter the fetus through placenta.  Order. Haemosporidians (Haemosporida) Blood parasites of vertebrates. The best known of the coccidians is Plasmodium, the causative organism of the most important infectious disease of humans malaria. The Plasmodium species are causing malaria Plasmodium falciparum. Plasmodium vivax. Plasmodium ovale. Plasmodium malariae. Malaria is a very serious disease, difficult to control and widespread, particularly in tropical and subtropical countries. More than 90% of the deaths worldwide occur in sub-Saharan Africa. In 2016, it was estimated that there were 216 million malaria cases and an estimated 445,000 deaths (WHO World Malaria Report, 2017). Life cycle of malaria parasites. Continuous cycling or delayed multiplication in the liver may cause periodic relapse over several years (1–2 years in P. ovale, 3–5 years in P. vivax). Relapse does not occur with P. falciparum, although a long prepatent period may occur, resulting in initial symptoms appearing up to 6 months or more after exposure. Citation: Chapter 46 Medical Parasitology, Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e; 2019. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=217776556&bookid=2629 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Malaria. Life cycle of Plasmodium vivax. (Reproduced with permission from Willey JM: Prescott, Harley, & Klein’s Microbiology, 7th edition. McGraw-Hill, 2008.) Citation: Chapter 51 Apicomplexa and Microsporidia, Ryan KJ. Sherris Medical Microbiology, 7e; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=176089100&bookid=2268 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Worldwide changes in malaria incidence 2000-2015:http://www.who.int/gho/malaria/en/ Geographic distribution of malaria. (Reproduced with permission from Willey J, Sherwood L, Woolverton C (eds): Prescott’s Principles of Microbiology. New York: McGraw-Hill, 2008; Data from World Health Statistics Quarterly 1988;41:69.) Citation: Chapter 51 Apicomplexa and Microsporidia, Ryan KJ. Sherris Medical Microbiology, 7e; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=176089100&bookid=2268 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Current distribution of malaria vectors: https://www.cdc.gov/malaria/about/biology/mosquitoes/map.html. Citation: Chapter 51 Apicomplexa and Microsporidia, Ryan KJ. Sherris Medical Microbiology, 7e; 2017. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=176089100&bookid=2268 Accessed: October 17, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved  Leucocytozoon (Leucocytozoonosis) Haemosporidian blood parasites of vertebrates, especially birds. Vectors are simuliid and Culicoides flies. Blood parasites of passerine birds, recorded worldwide.  Piroplasmosis This disease is a disease of Equidae (horses, donkeys, mules, and zebras), and is caused by two parasitic organisms, Babesia equi and Babesia caballi. Although, Equine Piroplasmosis is primarily transmitted to horses by ticks, this bloodborne disease has been spread mechanically from animal to animal by contaminated needles.  Phylum. Cnidosporidia Class. Myxosporidia Myxosporidia are obligate parasites characterized by spores comprised of several cells configured into one to seven spore shell valves, one to two amoeboid infective germs (sporoplasms), and two to seven nematocyst-like polar capsules, each of which contains a coiled extrudible filament with an anchoring function. The life cycle of myxosporidia is complex and incompletely understood for most species. Myxobolus pfeifferi – a disease of freshwater fish caused by a myxosporidian protozoan (Myxobolus pfeifferi) that invades connective tissue and muscles forming large tumorous masses and commonly causing the death of the host.  Myxosoma Myxobolus encephalicus infects the central nervous system of carp and can result in locomotory disorders. Myxobolus (= Myxosoma) cerebralis destroys head and vertebral column cartilage of juvenile salmonids and causes whirling disease, which can inflict heavy losses.  Phylum. Microsporidia Microsporidia are eukaryotic, unicellular organisms All microsporidia are obligate, spore-forming, intracellular parasites that invade vertebrates and invertebrates. Some species, however, have also been known to parasite those with health immune systems. Microsporidia are important parasites in fisheries, veterinary medicines and pest management.  Nosema bombycis Nosema bombycis, a microsproridian parasite, that causes a disease known as pébrine - so called because it produces pepper-like spots on the caterpillars. The disease is highly infectious and can pass from mother moth to her eggs, so it has long been a major concern for silkworm breeders.  Nosema apis Nosema apis (Zander) is a microsporidian, it is a small, single celled parasite affecting honey bees. It causes nosemosis, mainly known by the term nosema. Although parasitic, it is often thought of and talked about as a disease. A single spore can cause infection, but the mean infective dose is generally reported to be between 20 and 90 spores per bee. The symptoms can be confused with other honey bee problems, but they are genarally. Dysentery Shorter life of worker bees Lack of industry in the colony (slowness of development) Lower than normal propensity to sting Crawling bees Disjointed wings Distended abdomens  Genus. Glugea Glugea is a genus of microsporidian parasites, predominantly infecting fish. This disease is characterized by the formation of large cysts on the fish's body and in the internal organs. These cysts cause hypertrophy of the infected region (e.g., liver, gut, ovaries) and will burst, releasing infectious spores into the water. Eventually, the fish bloat, with tumor-like protrusions and eventually die.  Phylum. Ciliophora These are a group of diverse protozoans characterized by the presence of fine hair like cilia as locomotor structures. They are aquatic and free living or parasitic forms. Ciliates show a high degree of morphological and physiological specialisation compared to other animal like protistans. They possess specialised organelles that perform specific functions. The body is covered by a pellicle. Cilia may be found all over the body or restricted only to certain regions. Ciliates reproduce asexually by binary fission. Sexual reproduction is common. It occurs by a process called conjugation which involves exchange of genetic material between two individuals.  Class. Ciliata Ciliates are always multinucleate, possesing at least one macronucleus and one micronucleus, but varying from one to many of either type. The pellicle of ciliates may consist only of the cell membrane or in some species may form a thickened armor. Their structure is comparable to that of flagella, with axoneme and kinetosome, except that cilia are shorter.  Balantidiasis Balantidiasis is an infectious disease produced by a single-celled microorganism (protozoan) called Balantidium coli that infects the digestive tract. It is primarily a disease of the tropics, although it is also found in cooler, temperate climates. Most persons with balantidiasis do not exhibit any noticeable symptoms (asymptomatic), but a few individuals will develop diarrhea with blood and mucus and an inflamed colon (colitis).  Chilodonelliasis The ciliate Chilodonella cyprini. The parasites are able to swim freely, spreading easily from fish to fish. Reproduction by asexual division. The skin and gills become discolored, taking on an opaque, bluish-white to gray coloration. The area between the head and dorsal fin is generally the most severely affected. In advanced cases skin begins to swell, eventually shredding and falling off in strips. Gills are also affected and may be completely destroyed. Clamped fins, listlessness, hanging at the surface and gasping may also be seen.  Trichodiniasis Trichodina is a genus of ciliate protists that is ectocommensal or parasitic on aquatic animals, particularly fish. They are characterised by the presence of a ring of interlocking cytoskeletal denticles, which provide support for the cell and allow for adhesion to surfaces including fish tissue.  Ichthyophthiriasis Ichthyophthirius multifiliis is a ciliated protozoan which causes "Ich" or "white spot disease." This disease is a major problem to aquarists and commercial fish producers world wide. Ichthyophthirius is an important disease of tropical fish, goldfish, and food fish. The disease is highly contagious and spreads rapidly from one fish to another.  Study Questions 1. Protozoa. Their structure, biology, diversity and features of vital activity. 2. Phylum Sarcodina – biology and diversity. Order Amoebida – biolody, diversity. Entamoeba histolytica – structure, life cycle. 3. Phylum Mastigophora. Their biology, variety and diseases: Trypanosoma brucei gambriense, Trypanosoma cruzi, Leishmania - structure, life cycle. 4. Phylum Sporozoa. Their biology, variety and practical meaning in livestock: 1. Order. Coccidiida: Coccidia and Toxoplasma gondii - structure, biology, life cycle. 2. Order. Haemosporida: Plasmodium - structure, biology, life cycle. 5. Microsporidia. Their biology and meaning. Microsporidias – insect pests, their meaning (In general). 6. Structure of phylum Cnidosporidia. Their reproduction and meaning (In general).  SUMMARY Protozoa Protozoa are one-celled animals found worldwide in most habitats. Most species are free living, but all higher animals are infected with one or more species of protozoa. Infections range from asymptomatic to life threatening, depending on the species and strain of the parasite and the resistance of the host. Structure Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. Some protozoa have structures for propulsion or other types of movement. Classification On the basis of light and electron microscopic morphology, the protozoa are currently classified into six phyla.  SUMMARY Life Cycle Stages The stages of parasitic protozoa that actively feed and multiply are frequently called trophozoites; in some protozoa, other terms are used for these stages. Cysts are stages with a protective membrane or thickened wall. Protozoan cysts that must survive outside the host usually have more resistant walls than cysts that form in tissues. Reproduction Binary fission, the most common form of reproduction, is asexual; multiple asexual division occurs in some forms. Both sexual and asexual reproduction occur in some. Nutrition Nutrition is holozoic or authotrophic. Literature Yaeger RG. Protozoa: Structure, Classification, Growth, and Development. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 77. Available from: https://www.ncbi.nlm.nih.gov/books/NBK8325/ Druger, M., Anderson, O. R., Society of Protozoologists, & National Science Teachers Association. (2000). Explore the World Using Protozoa. National Science Teachers Association. Englund PT, Sher A (eds): The Biology of Parasitism. A Molecular and Immunological Approach. Alan R. Liss, New York, 1988. Goldsmith R, Heyneman D (eds): Tropical Medicine and Parasitology. Appleton and Lange, East Norwalk, CT, 1989. Lee JJ, Hutner SH, Bovee EC (eds): An Illustrated Guide to the Protozoa. Society of Protozoologists, Lawrence, KS, 1985. Kotler DP, Orenstein JM. Prevalence of Intestinal Microsporidiosis in HIV-infected individuals referred for gastrointestinal evaluation. J Gastroenterol. 1994;89:1998. Neva FA, Brown H: Basic Clinical Parasitology, 6th edition, Appleton & Lange, Norwalk, CT, 1994. https://parasite.org.au/para-site/contents/protozoa-intoduction.html Sherris Medical Microbiology, 7e Kenneth J. Ryan. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. Stefan Riedel, Jeffery A. Hobden, Steve Miller, Stephen A. Morse, Timothy A. Mietzner, Barbara Detrick, Thomas G. Mitchell, Judy A. Sakanari, Peter Hotez, Rojelio Mejia Review of Medical Microbiology & Immunology: A Guide to Clinical Infectious Diseases, 16e Warren Levinson, Peter Chin-Hong, Elizabeth A. Joyce, Jesse Nussbaum, Brian Schwartz Current Medical Diagnosis & Treatment 2021. Maxine A. Papadakis, Stephen J. McPhee, Michael W. Rabow www.lsmu.lt